Aerosol delivery during invasive ventilation : an in vitro analysis and in vivo radioisotopic investigation

The objective of the thesis was to evaluate the aerosol delivery to the lungs with two ventilation modes (volume control vs pressure support mode) during invasive ventilation considering that the inspiratory flow pattern differ between both modes (constant vs decelerating flow pattern). Aerosol delivery with a vibrating-mesh nebulizer was assessed in vitro using the residual gravimetric method and in vivo using planar scintigraphy. Volume controlled ventilation was associated to higher lung doses of radiolabel delivered to ventilated patients (15 vs 10% of the initial dose) in comparison pressure support ventilation (lower and uncontrolled respiratory rate, higher inspiratory flow). It confirmed the interest to apply a constant inspiratory flow of 30 L/min to increase aerosol delivery suggested in vitro in comparison to a decelerating flow (peak of 60 L/min). There is a benefit to control the breathing pattern during the nebulization. However, a systematic review reported a lung deposition inferior to 20% of the initial dose in invasive ventilation. Further studies are needed to improve the administration technique.